Reinforcing steel of the same type and grade shall be used for the main reinforcement in a structure. However, for primary and secondary reinforcements it is permissible to use two different types or grades of steel simultaneously.
Bars may be arranged individually, or in pairs, in contact, or groups of three or four bars bundled in contact. Bundled bars shall be closed with stirrups or ties. Bundled bars shall be tied together to ensure they remain together. Bars larger than 32 mm diameter shall not be bundled other than columns.
The calculated tension or compression in any bar at any section shall be developed on each side of the section by an appropriate development length or end anchorage or by a combination thereof.
Development Length of Bars: The development length Ld is given by Ld = (ǿσs)/4τbd
Where ǿ = nominal diameter of the bar,
σs = stress in bar at the section considered at design load, and
Ƭhd = design bond stress
The anchorage length of the straight bar in compression shall be equal to the development length of bars in compression as specified. The projected length of hooks, bends and straight lengths beyond bends if provided for a bar in compression, shall only be considered for development length.
For this clause the diameter of a round bar shall be its nominal diameter and in the case of bars which are not round or in the case of deformed bars or crimped bars, the diameter shall be taken as the diameter of the circle given an equivalent effective area. Where spacing limitations and minimum concrete cover are based on the diameter. A group of ban bundled in contact shall be treated as a single bar of diameter derived from the total equivalent area.
Nominal cover is the design depth of concrete cover to all-steel reinforcements, including links. It is the dimension used in the design and indicated in the drawings. It shall be not less than the diameter of the bar.
|Column Dimension (b or D)||Minimum Wall Thicknt.u|
|Fire Resistance (h)||Maximum Beam Width(b)||Rib Width of Slubs (b)||Minimum Thickness of Floors (D)||Fully Exposed||50% Exposed||one Face Exposed||p < 0.4%||0.4% < p < 1%||p > 1%|